US6464934B2 - Method for manufacturing a rare earth element—iron—boron permanent magnet - Google Patents
Method for manufacturing a rare earth element—iron—boron permanent magnet Download PDFInfo
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- US6464934B2 US6464934B2 US09/771,806 US77180601A US6464934B2 US 6464934 B2 US6464934 B2 US 6464934B2 US 77180601 A US77180601 A US 77180601A US 6464934 B2 US6464934 B2 US 6464934B2
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- alloy
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- rare earth
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Hard Magnetic Materials (AREA)
Abstract
In a method for manufacturing a permanent magnet, a powder of a magnetic base alloy and powders of at least two binder alloys are mixed. The magnetic base alloy has a general formula SE2T14B, wherein SE is at least one rare earth element, including Y, and T is Fe or a combination of Fe and Co, wherein Co does not exceed 40 wt % of the combination of Fe and Co. The two binder alloys have respective general formulas SE6(Fe,Co)13−xGa1+x and SE2Co3. The base alloy and the at least two binder alloys are mixed in a weight ratio between 99:1 and 89:11. The mixture is then compressed and is subsequently sintered in a vacuum and/or in an inert gas atmosphere.
Description
This application is a continuation-in-part of U.S. patent application 09/254,409 filed Mar. 5, 1999, now abandoned which is a 371 of application Ser. No. PCT/OE97/01787, filed Aug. 19, 1997.
1. Field of the Invention
The present invention is directed to a permanent magnet of the type SE-Fe—B that has the tetragonal phase SE2Fe14B as the principal phase, wherein SE is at least one rare earth element, including Y.
2. Description of the Prior Art
A magnet of the above general type is disclosed, for example, in European Application 0 124 655 and in U.S. Pat. No. 5,230,751 that corresponds therewith. Magnets of the type SE-Fe—B exhibit the highest energy densities currently available. SE-Fe—B magnets manufactured by powder metallurgy contain approximately 90% of the hard-magnetic principal phase SE2Fe14B.
German OS 41 35 403 discloses a two-phase magnet, wherein the second phase can be a SE-Fe—Co—Ga phase.
U.S. Pat. No. 5,447,578 discloses a SE-transition metal-Ga phase.
One usually proceeds such in the manufacture of such SE-Fe—B magnets by combining a SE-Fe—B base alloy with a composition close to the SE2Fe14B phase and a binder alloy with a lower melting temperature. The goal is to set the structure of the SE-Fe—B sintered magnets of SE2Fe14B base alloys with inter-granular binders, while using optimally little binder alloy.
It has now turned out that the proportion of this binder alloy in the mixture of the base alloy must lie within 7-10 weight %. In this mixing range, sinter densities of approximately ρ>7.55 g/cm3 are achieved only at sintering temperatures above 1090° C. These sinter densities roughly correspond to 99% of the theoretical density. Outside this mixing range, the sinterability and, thus, the remanence that can be achieved are considerably influenced. The grain growth is highly activated in the magnets with a proportion of this binder alloy of more than 10 weight %, but the pores are not closed. The consequence is the formation of a structure with anomalously large grains (>50 μm) and with high porosity as well as with low sinter densities. Given lower proportions of binder alloy, the amount of the fluid phase is accordingly not adequate for the densification.
It is an object of the present invention to provide a powder-metallurgical manufacturing method for permanent magnets of the SE-Fe—B type that exhibits an enhanced sinterability upon reduction of the proportion of binder alloy compared to the known methods and also achieves a very good remanence.
The object is inventively achieved by a method that comprises the following steps:
a1) a powder of a base alloy of the general formula
wherein SE is at least one rare earth element, including Y, and T is Fe or a combination of Fe and Co, whereby the Co part does not exceed 40 weight % of the combination of Fe and Co,
a2) and powders of at least two binder alloys of the general formulas
and
SE2CO3
wherein SE is at least one rare earth element, including Y, and wherein 0≦x≦2, are mixed in a weight ratio of 99:1 to 89:11;
b) the mixture is compressed and, subsequently,
c) is sintered in a vacuum and/or in an inert gas atmosphere.
It has been shown that permanent magnets manufactured in this way exhibit very high remanences, and that the proportion of binder alloy compared to the proportion of the base alloy can be reduced to below 7 weight %. Further, the additional gallium-containing phase of the binder alloy exhibits especially good wetting properties.
FIG. 1 shows the demagnetization curve exhibited by a magnet made in accordance with the inventive method, at room temperature.
FIG. 2 shows the demagnetization curve of a magnet manufactured according to the conventional powder-metallurgical method.
The invention is explained in greater detail below on the basis of the exemplary embodiments and the figures. A Nd2Fe14B base alloy and five binder alloys with the following compositions were employed for the investigations:
TABLE 1 | ||||||
B-alloy 1 | B-alloy 2 | B-alloy 3 | B-alloy 4 | B-alloy 5 | Base All. | |
SV | SV | SV | SV | SV 95 | SV | |
Element | 95/130 | 95/131 | 95/132 | 95/133 | 134 | 96/138 |
SE | 50.9 | 47.7 | 64.8 | 51.5 | 50.3 | 28 |
|
0 | 0 | 0 | 0 | 0 | 28 |
Pr | 50.9 | 31.7 | 0 | 51.5 | 50.3 | 0 |
|
0 | 15.7 | 64.8 | 0 | 0 | 0 |
Co | 23 | 24.65 | 35.2 | 0 | 45.44 | 0 |
Ga | 4.2 | 4.5 | 0 | 4.25 | 4.15 | 0 |
|
0 | 0 | 0 | 0 | 0 | 1.03 |
Fe | 21.9 | 0 | 0 | 44.25 | 0 | 70.97 |
Alloy | Pr6(Fe, | Pr,Dy6(Fe, | Dy2Co3 | Pr6Fe13Ga | Pr6Co13Ga | Nd2Fe14B |
Type | Co)13Ga | Co)13Ga | ||||
The following mixtures were prepared of coarse powders of these alloys.
TABLE 2 | ||||||
Part | B-alloy 1 | B-alloy 2 | B-alloy 4 | B-alloy 5 | Base All. | |
(Wt. %) | (Wt. %) | (Wt. %) | B-alloy 3 | (Wt. %) | (Wt. %) | (Wt. %) |
|
5 | 5 | 1 | 89 | ||
|
0 | 5 | 0 | 5 | 0 | 90 |
Mixture 3 | 5 | 2.5 | 1 | 1.5 | 1 | 89 |
|
6 | 0 | 1.5 | 2.5 | 0 | 90 |
Mixture 5 | 6.5 | 1 | 1.5 | 1 | 1 | 89 |
|
5.5 | 0 | 1.5 | 3 | 0 | 90 |
Mixture 7 | 5 | 1 | 1.5 | 2.5 | 1 | 90 |
|
3.5 | 2 | 1 | 3.5 | 0 | 90 |
The calculated composition of the manufactured magnets then yield:
TABLE 3 | |||||||||
Magnet | No. 1 | No. 2 | No. 3 | No. 4 | No. 5 | No. 6 | No. 7 | No. 8 | Ref. |
SE | 30.1 | 30.3 | 30.35 | 30.35 | 30.4 | 30.7 | 30.5 | 30.6 | 30-31 |
Nd | 25.2 | 24.9 | 25.2 | 25.2 | 25.2 | 24.9 | 25.2 | 24.9 | 27-28 |
Pr | 4.13 | 4.6 | 4.1 | 4.1 | 4.14 | 4.85 | 4.15 | 4.7 | 1.7-2.2 |
Dy | 0.79 | 0.79 | 1.04 | 1.05 | 1.2 | 0.97 | 1.3 | 0.96 | 0.6-1.4 |
Co | 2.4 | 1.7 | 2.1 | 2.1 | 2.25 | 2.25 | 1.9 | 2.1 | 0.8-2 |
Ga | 0.435 | 0.48 | 0.38 | 0.38 | 0.36 | 0.4 | 0.36 | 0.43 | 0.1-0.4 |
B | 0.93 | 0.92 | 0.93 | 0.92 | 0.93 | 0.92 | 0.92 | 0.92 | 0.95-0.98 |
Fe | Bal. | Bal. | Bal. | Bal. | Bal. | Bal. | Bal. | Bal. | Bal. |
The mixtures were finely ground in a planetary ball mill for 90 minutes; the average particle size of the fine powder achieved 2.9 to 3.0 μm. Anisotropic, isostatically pressed magnets were manufactured from the fine powders. They were sintered to densities of ρ>7.50 g/cm3 and subsequently tempered.
FIG. 1 shows the demagnetization curve of the magnets 1-8 at room temperature.
For comparison, a magnet according to the prior art of a binder alloy with the composition of approximately 28 weight % Nd, 0.5 weight % Dy, 2.0 weight % Pr (sum SE≈30.5 weight %), 0.98 weight % B, 0.03 weight % Co and balance Fe was manufactured with the analogous powder-metallurgical method. The same base alloy as in the magnets 8-1 was employed as the base alloy.
FIG. 2 shows the demagnetization curve of this magnet that has been manufactured according to the conventional powder-metallurgical method according to the prior art.
It can be clearly seen that the inventive permanent magnets exhibit a significantly more favorable demagnetization curve at room temperature than permanent magnets that have been manufactured according to the prior art.
The highest coercive field strength was achieved with magnet 322/1 after a tempering at a temperature of 630° C. The magnet 322/1, which was sintered at a temperature of 1080° C., achieved a coercive field strength of 10.4 kOe, whereby its remanence amounts to 1.41 T. An alignment degree of the grains of 96% was measured in this magnet, and the relative density amounts to 98%. Computationally, a remanence of 1.415 T is thereby to be expected, i.e. a very good coincidence with the measured value.
The present invention presents a new boron-free and iron-free binder alloy with the composition SE5(Co, Ga)3 or manufacturing permanent magnets. The melting temperature of this binder alloy lies at approximately 530° C.
The employment of these binder alloy mixtures for the powder-metallurgical manufacture of permanent magnets exhibits considerable advantages over the individual binder alloys.
The proportion of binder alloy can thus be decidedly reduced compared to the proportion of binder alloys according to the prior art, i.e. to a proportion below 7 weight %.
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
Claims (2)
1. A method for manufacturing a permanent magnet, comprising the steps of:
a1) mixing a powder of a magnetic base alloy of a general formula
wherein SE is at least one rare earth element, including Y, and T is selected from the group consisting of Fe and a combination of Fe and Co, whereby the Co part does not exceed 40 weight % of the combination of Fe and Co,
a2) and powders of at least two binder alloys of respective general formulas
and
wherein 0≦x≦2, in a weight ratio to obtain a mixture between 99:1 to 89:11;
b) comprising the mixture to obtain a compressed mixture and;
c) sintering the compressed mixture in an environment selected from the group consisting of a vacuum and an inert gas atmosphere.
2. A method according to claim 1 , wherein the step of mixing comprises mixing said base alloy and said binder alloys in a weight ratio of base alloy to binder alloys between 99:1 and 93:7.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/771,806 US6464934B2 (en) | 1996-09-06 | 2001-01-29 | Method for manufacturing a rare earth element—iron—boron permanent magnet |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19636283A DE19636283A1 (en) | 1996-09-06 | 1996-09-06 | Process for manufacturing a SE-FE-B permanent magnet |
DE19636283 | 1996-09-06 | ||
DE19636283.0 | 1996-09-06 | ||
US25440999A | 1999-03-05 | 1999-03-05 | |
US09/771,806 US6464934B2 (en) | 1996-09-06 | 2001-01-29 | Method for manufacturing a rare earth element—iron—boron permanent magnet |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DE1997/001787 Continuation-In-Part WO1998010438A1 (en) | 1996-09-06 | 1997-08-19 | METHOD FOR THE MANUFACTURE OF A RARE EARTH ELEMENT (SE)-Fe-B PERMANENT MAGNET |
US25440999A Continuation-In-Part | 1996-09-06 | 1999-03-05 |
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US20010006605A1 US20010006605A1 (en) | 2001-07-05 |
US6464934B2 true US6464934B2 (en) | 2002-10-15 |
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US20090114650A1 (en) * | 2007-11-01 | 2009-05-07 | Houston Jr Michael Roderick | Compartment container |
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CN101894646A (en) * | 2010-07-14 | 2010-11-24 | 麦格昆磁(天津)有限公司 | High-performance anisotropic magnetic material and preparation method thereof |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6027576A (en) * | 1996-09-06 | 2000-02-22 | Vacuumschmelze Gmbh | Rare earth element-iron-boron permanent magnet and method for the manufacture thereof |
US6254659B1 (en) * | 1996-09-06 | 2001-07-03 | Vacuumschmeleze Gmbh | Rare earth - iron -boron permanent magnet and method for the manufacture thereof |
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Publication number | Priority date | Publication date | Assignee | Title |
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US6027576A (en) * | 1996-09-06 | 2000-02-22 | Vacuumschmelze Gmbh | Rare earth element-iron-boron permanent magnet and method for the manufacture thereof |
US6254659B1 (en) * | 1996-09-06 | 2001-07-03 | Vacuumschmeleze Gmbh | Rare earth - iron -boron permanent magnet and method for the manufacture thereof |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US20090114650A1 (en) * | 2007-11-01 | 2009-05-07 | Houston Jr Michael Roderick | Compartment container |
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